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Nov. 15, 2011 -- Women who often have trouble falling asleep or staying asleep may have an increased risk of fibromyalgia, a new study from Norway reveals.

"Our findings indicate a strong association between sleep disturbance and fibromyalgia risk in adult women," study researcher Paul Mork, PhD, says in a news release. He is an associate professor in the department of human movement science at the Norwegian University of Science and Technology in Trondheim, Norway.

Norwegian researchers also found that women who had the most severe sleep complaints -- they often or always had difficulty nodding off -- had a greater chance of developing fibromyalgia. This link was somewhat stronger in middle-aged and older women than it was in younger women.

The researchers followed 12,350 Norwegian women aged 20 and older over a 10-year period. The women were all participants in a large nationwide health survey, and they had a physical exam and completed a questionnaire describing their medical history upon enrolling.

At the beginning of the study, researchers asked women about their sleep habits, including whether they had difficulty falling asleep or staying asleep and how often these problems occurred. None of the participants regularly took sleeping pills.

All of the women were free of pain or stiffness in their muscles or limbs when the research got under way, and they had no movement disorders.

Poor Sleep and Fibromyalgia

Ten years after enrolling in the study, researchers found that 327 women had been diagnosed with fibromyalgia. A little more than 3% of women aged 20-44 were diagnosed with the condition, and nearly 2% of women aged 45 and older.

The researchers noticed that women who frequently reported having trouble sleeping a decade earlier had a greater chance of being diagnosed with the chronic pain condition.

Women aged 45 and older who often or always had difficulty sleeping had more than a fivefold increase in their risk of fibromyalgia, compared to women who had no problems sleeping. Younger women aged 20 to 44 who had the most trouble getting enough shut-eye had a threefold increase in their risk of the disorder.

"The exact mechanisms by which poor sleep can cause widespread musculoskeletal pain are uncertain," the researchers write. They encourage additional studies to explore whether detecting and treating sleep problems early can lessen the chances of developing chronic widespread pain.